Such a front jaw is described, for example, in EP-A2 0 408 855. In this known solution, both the relief of the toggle levers during upwardly acting forces and also the release movement of the jaw during a backward twisting fall is accomplished by a tilting of a bearing part relative to the jaw housing. The sole down-holding means is adapted to the respective shoe sole thickness by moving the bearing part along the rear crosswall of the jaw housing, with additional sloped surfaces being provided for this purpose on the housing and bearing part.
This solution is by all means practical, however, friction occurs inevitably at the contact surfaces during movement of these structural parts.
A slightly different front jaw is known from DE-OS 37 34 492, in which the sole holder is adjusted and relieved also by a movement, namely along a sloped surface of the housing. The already abovementioned disadvantage is thereby created.
An object of the invention is to bring help mere and to provide, in a front jaw of the abovementioned type, a mechanism for facilitating an automatic adaptation of the front jaw to the respective shoe sole thickness so that as little as possible friction will occur.